A challenge faced by the telecommunications industry is the high cost of installing optical fibre between the provider and the end customer. Some of the highest costs are incurred in the so-called “last mile” of installation, namely the installation of lines to individual customers and limited groups of customers, often within urban areas. In particular, as customers are added to a network, the generation of a new branch line can be difficult and costly, often requiring the installer to make a splice or junction with the trunk line and to provide loops of surplus cable at predetermined locations in advance when installing the initial trunk lines. With the rapidly growing need for high-speed data connections to businesses and residences (driven mainly by the need to access the Internet) a faster and more economical method is needed for installation of cable networks, especially within new and growing residential and commercial areas.
Optical cables are typically buried, which can present difficulties when it is desired to expand a network. Typically, when a cable network is installed within a new housing or business/industrial development, many of the occupants will not initially require a cable connection and indeed, a house or building may not yet exist at many addresses when the network is initially installed. Typically, when a customer subsequently orders a cable-delivered service (such as internet or video services) it becomes necessary to install a cable to the residence. Desirably, this is accomplished with a minimum of difficulty.
The need to service future customers may be met by pre-installing “dark line” at suitable locations within the cable network, which may be extracted and converted into “lit line” when a new customer is added to the network. However, it can be difficult to conveniently store suitable lengths of dark line within the network at suitable locations. There is thus a need for systems to store such lengths of dark line within an installed network, which may then be conveniently extracted when needed.
One approach for an inexpensive and simple means to install fibre optic cable is within a shallow slot-like trench cut into an upper layer of pavement or the like, for the laying of a cable within or immediately under a street or other surface. The trench may be cut with a single pass of a slab saw. Such a system is best employed when combined with a convenient means to form junctions or branches within the cable system leading to individual users. In conventional cable-laying systems or methods, the forming of a branching network requires considerable additional excavation and other labour in order to install conventional junction boxes or the like and to form a splice at the junction.
The need for a convenient way to expand a network by adding branches requires an easy means to provide a branch line of cable without requiring the labour-intensive job of splicing in new cables to meet growing system needs. The present inventor has previously developed systems for storing of surplus cable for such future use at intersection points or other nodes, for example as loops of cable which is stored within a buried housing, in combination with a convenient junction box. However, in some situations it is more convenient to supply lengths of dark cable in uncoiled form, within the trunk conduit alongside the lit cables such that a suitable length dark cable may be withdrawn from the conduit when required. It has hitherto been difficult to provide a system that conveniently permits this.
It is desirable to provide a system and method for storing and routing fibre optic cables that meet the following needs:    a) the ability for the cables and system components to fit within a narrow slot-like trench or cut;    b) reduced requirement for cable loops that must be stored within additional buried containers for future system expansion; and    c) reduced requirement to form cable splices at the branch junction locations.
Buried fibre optic cable networks generally comprise trunk and branch lines, which intersect at a plurality of nodes. The branch lines may lead to collection points, or to individual houses or buildings. Within certain segments, trunk and branch lines may coincide, for example where it is necessary for branch lines to backtrack over the route of a trunk line, i.e., “back-haul” segments.
A drawback of current network systems for storing and routing cables within substrates is that the complexity of the network can require the installer to provide either a relatively wide cut for installation of multiple lines, or a series of parallel cuts. This need can arise to accommodate back-haul lines. In the past, back-haul lines have been installed within parallel cable ducts alongside the trunk line. However, parallel ducts of this type require additional space within the surface cut or additional cuts, making installation more difficult and costly.
Trunk lines conventionally include a cable that includes a large number of optic fibres bound by an external sheath, which is relatively rigid so as to protect the fibres from breaking or crushing. Cables of this type typically range in size from approximately 6 mm in width, comprising 72 fibres, to about 25 mm in width, bundling 800 fibres.
It is also known to install optical fibres via blowing of fibres through hollow tubes. For this purpose, a hollow tube having a relatively narrow diameter is provided, with individual optical fibre (cables) being blown through the tube. This installation method has the advantage that it is relatively easy to provide optical fibres within a pre-installed network, for example, to supply an optic fibre to a new customer. Optic fibre blowing offers flexibility, although it is best suited for relatively short distances. For this reason, it is best suited for use in branch lines, or short portions of trunk lines. As well, optic fibre blowing is best suited for installing a limited number of optic fibres within a single tube. Thus, this installation method is not well suited for large trunk lines containing a large number of individual fibres. One drawback of blowing tubes is their bulk, in that the tube diameter makes it difficult to accommodate multiple tubes and cables within a single narrow cut or channel, particularly tubes and cables having different diameters. It is useful to provide a fibre optic network which permits a combination of bundled fibres, including bundled fibres of different diameters, and blowing tubes for blowing of optical fibres where appropriate.
The present inventor has previously described in WO/2002/065182 a system for a fibre optic network consisting essentially of relatively narrow channels cut within a surface, such as a road. Within this type of system, many of the network components are installed within narrow channels, including trunk lines, branch lines and optionally some or all of the nodes. It is simple to install such a system wherein the trunk and branch lines are installed within relatively narrow road cuts which can be easily restored after the cables are installed within the channels. The cut may be made by a single pass of a slab saw. For use in a system of this type, the inventor has developed a cable protector which is well suited for surface inlay installations. In the surface inlay method, all components of the network are surface installed by vertical inlay of the cable and associated components (conduits, junction housings etc.). There is no need to thread individual cables through any component of the network. All components of the network may be assembled on-site or in advance. The surface inlay method permits components to be installed around uncut lengths of cable; there is no need to cut a cable so as to generate a free end for threading through any component. The entire network may then be simply inlayed piecemeal into the cut, without any threading of cables through any component of the system.
One of the components of such a system is the narrow profile protective conduit described in the inventor's U.S. Pat. No. 6,807,355, which is incorporated herein by reference. This type of conduit is configured to retain multiple cables in a narrow stacked array within the conduit interior. This type of conduit is particularly useful for surface inlay installation of cables within a narrow channel or cut made within a surface.
Several patents have been issued for technology relating to electrical and optical fibre cable installations.
One example is U.S. Pat. No. 5,879,109 issued to Finzel, et al. which provides a complex process for installing optical or electrical cable into solid surfaces such as asphalt. The method uses a slow moving apparatus to heat the ground surface until it has softened. A channel-forming unit is subsequently used to introduce a channel into the heated ground by displacing the ground material alongside the channel border. A laying unit is then used to introduce the optical or electrical cable into the channel, followed by a filling unit which is used to reintroduce the displaced ground material back into the channel and then rolled to compact the ground material which has been reintroduced into the channel.
U.S. Pat. No. 6,065,902 issued to Mayr, et al. provides a method and apparatus for on-site production and installation of optical fibre cable at the location for placing. This method seeks to reduce transportation costs and quantity of material required for large-scale optical fibre cable installations.
Canadian patent no. 2,237,324 to Zeidler et al. discloses a method for laying a fibre optic cable of between 2 mm and 10 mm within a narrow channel having a width slightly wider than the cable. The cable is introduced into the channel by means of a cable feed device, and the channel is then filled with infill material by a filling device which moves along in a coordinated fashion with the laying device. The laying channel extends into the top several layers of a paved surface and is between 4 cm and 15 cm in depth, with 7 cm being identified as ideal.
There is a need for a convenient arrangement for forming cable junctions. There is a need to easily provide slack in the installed cable to accommodate junctions, system expansions and repairs. There is a further need to easily accommodate a variety of surfaces including pavement, sidewalks, vertical walls, unpaved surfaces such as sod, etc.